A moment of clarity followed by the realization of just how shitty a given situation truly is. Commonly follows the act of undertaking a task, usually work related, and once fecal lucidity is achieved it is punctuated by the phrase "Oh, fuck!", "Fuck me!", or "Shitty shit shat!"

When Tim was assigned the task of recording company account spenditures he was elated but after going through expense reports and other financial records he had a moment of fecal lucidity, screamed "fuck me!", and ran to the closest bar to get blotto.

Jim got home from work to Cindy's litany of how badly the kids were behaving, but fortunately for them, they were in luck. Jim could not concentrate on a single word with the turtle head poking out. Once he was done dumping he achieved a level of unmatched fecal lucidity.
"So," sighed Jim deeply, walking out of the bathroom, "Anything interesting happen today?"

Clarity, especially mental clarity, that one is completely and totally wallowing in shit.

"I've been working on a project for my boss all week and last night I had a moment of fecal lucidity. There is no fucking way I will be able to complete it by the deadline because I have no clue what I am doing!" -Me